Hormones

Question 1

Define hormones

Answer 1

• chemically released by specific glands in the body to regulate medium and long term changes in the body.
• They are produced and released by the endocrine system directly into the bloodstream and will travel to their target cells where they have receptors that enable them to interact with the cells to produce an effect that either increases or decreases its function.

Question 2

What is the hormone and behaviour involved in the Schochat et al (1997) and Sack et al (2000)
[Name/Location/Function/Behaviour]

Answer 2

Melatonin
Location: Produced in the Pineal gland
Function/behaviour: Melatonin is a naturally occurring hormone, its both endocrine (enters the bloodstream from a pineal gland) and paracrine (signalling phenomenon, as the light is low in retina, it signals “time to sleep”).
- The lack of light is detected by optic nerve.
- The darkness elicit electrical stimulation in the pineal gland and increase melatonin levels.
- It’s a sleep hormone, regulates body’s internal clock increase is just before bed and begins to suppress as a person wakes up.

Question 3

Aim of Sack

Answer 3

To investigate whether a daily dose of melatonin could entrain blind individual’s circadian rhythms to a normal 24-hour cycle.

Question 4

Method of Sack

Answer 4

Seven totally blind subjects who had free-running circadian rhythms.
Participants were given 10 mg of melatonin or placebo daily, one hour before their preferred bedtime, for three to nine weeks.
Sleep was monitored by EEG, oxygen measures; EOG & EMG (eye and muscle measurement).

Question 5

Findings of Sack

Answer 5

• the blind participants had free-running circadian rhythms with cycles averaging 24.5 hours
• These rhythms were unaffected by the administration of placebo.
• In six of the seven participants the rhythm was entrained to a 24.0-hour cycle during melatonin treatment.
• the participants spent less time awake after the initial onset of sleep and the efficiency of sleep was higher.
• The dose was then reduced to 0.5 mg per day over a period of three months; the entrainment persisted, even at the lowest dose.

Question 6

Conclusion of Sack

Answer 6

Administration of melatonin can entrain circadian rhythms in most blind people who have free-running rhythms.

Question 7

Aim of Schochat

Answer 7

To investigate the involvement of Melatonin in the sleep-wake cycle

Question 8

Method of Schochat

Answer 8

• Six male participants in sleep laboratory for 29 hours.
• Used a very short sleep-wake paradigm, participants spent 7 minutes in every 20 minutes lying down trying to sleep in a darkened room.
• At different times throughout the day they measured participants tendency to sleep and melatonin levels by taking blood samples.

Question 9

Findings of Schochat

Answer 9

Demonstrated a close and precise relationship between propensity to sleep and melatonin levels

High levels of melatonin = greater propensity to sleep. Increase melatonin = increased tendency to sleep

Question 10

Conclusion of Schochat

Answer 10

Evidence that there is a relationship between melatonin increase and propensity to sleep.